Cryogenic liquid handling system

ABSTRACT

A cryogenic liquid handling system for infrared detection or the like having a cryogenic liquid supply container which is insulated in part by the flow of cryogenic vapor existing above the liquid level, a two phase flow generator in the container, a heated delivery line to maintain the two phase flow and a separator at the point of use, including a vapor feedback passage to prevent the formation of frost in the lens of the infrared detection system.

llnited States Patent 11 1 Massey 1 May 1, 1973 [5 CRYOGENIQ LIQUIDHANDLING 3,006,157 10/1961 Haettingeret a]. ..62/DlG. 19 SYSTEM3,120,600 2/1964 True ..I38/32 x 3,122,004 2/1964 Abe le ..62/D1G. 19Inventor: Alton y, 485 Fries Road, 3,126,711 3/1964 M11121 ..62/55 xTonawanda, NY 14150 3,203,477 8/1965 Collard ..62 259 [22] Filed: y 26,1971 3,548,607 12/1970 Plllsbury, Jr. et a1 ..62/52 [21] Appl. No.:146,903 Primary Examiner-Meyer Perlin Assistant ExaminerR0nald C.Capossela 52 us. c1. ..62/51, 62/55, 138/33, Mama-Allen "affe 62/128,62/514, 62/DIG. 19 51 1111. C1. ,.Fl7c 7/02 [57] ABSTRACT [58] Field ofSearch ..62-/50.l, 514, 55, A cryogenic liquid handling system forinfrared detec- 3 tion or the like having a cryogenic liquid supplycontainer which is insulated in part by the flow of [5 R f r n es C tcryogenic vapor existing above the liquid level, a two phase flowgenerator in the container, a heated UNITED STATES PATENTS delivery lineto maintain the two phase flow and a 3,418,822 12/1968 Massey ..62 55 pat r at t point of u ng a ap r f d- 3,378,673 4/1968 back passage toprevent the formation of frost in the 2,707,377 5 lens of the infrareddetection system. 3,258,602 6/1966 2,244,635 6/1941 Williamson, Jr..l38/103 21 Claims, 1 Drawing Figure Patented May 1, 1973 3,729,946

v CONTROL 2;

" 8 INVENTOR.

AmNAMmY ATTORNEY.

1 CRYOGENIC LIQUID HANDLING SYSTEM BACKGROUND OF THE DISCLOSURE Thepresent invention relates to fluid handling systems and, moreparticularly, to an improved cryogenic fluid handling system. In myprior US. Pat. No. 3,418,822 a system is disclosed for transporting astream of cryogenic liquified gas which is based on the Leidenfrostphenomena. According to the teachings of my prior patent, the cryogenicliquified gas is transported through a flexible or semi-rigid conduitwithout the usual deterioration thereof due to the low temperatures ofthe liquified gas. This is accomplished by converting a portion of thecryogenic liquid into a gaseous phase which surrounds the remainingliquid creating separate liquid spheroids which are propelled throughthe conduit by the gas. Near the point of use the gas is separated fromthe liquid spheriods whereby the liquid can be employed for its intendedcooling purposes such as cryogenic surgery or infrared detection or thelike.

The creation of the gas-liquid or two phase flow is accomplished. by theapplication of heat in the conduit near the source of cryogenic liquidsupply. Once the two phase flow is created it must be maintained. In myprior patent the maintenance of such flow is accomplished by the heatadded to the conduit by the environment. Thus, my prior system must bedesigned with a precise knowledge of the environment for most efficientoperation. Should environmental conditions change either in temperatureor pressure, the efficiency of my prior system is significantlyeffected. For example, if the temperature increases more gas phase isproduced resulting in less usable liquid. Should the environmentaltemperature decrease significantly, as it would in space applications,less heat is supplied by the environment to the conduit which, in turn,supplies less heat to the vapor phase thereby reducing the shieldingeffect for the liquid spheroids. These spheriods would thus come intocontact with the relatively hot conduit walls and would vaporize. Thisaction would repeat until most of the liquid has vaporized and little orno liquid would be left to perform a useful cooling function.Additionally, since the conduit walls looses heat to the spheroids andthe vapor, the temperature thereof is reduced until its low temperatureproperties are reached, whereupon deterioration takes place. It istherefore necessary for efficient operation of the system that the heatadded to the conduit must be just that necessary for the maintenance ofthe two phase flow in just the right proportions; where theenvironmental conditions change it is not possible with my prior systemto achieve such a balance.

SUMMARY OF THE INVENTION The foregoing disadvantages, as well as other,of prior systems are overcome according to the teachings of the presentinvention which provides an improved cryogenic fluid handling systemthat is simple, efficient, inexpensive, independent of environmentalconditions, versatile and noise-free.

According to one aspect of the present invention a nonvacuum insulatedcryogenic supply container incorporates a heat shield in the form of aheat exchanger having one end in communication with the vapor space inthe container and the other end in communication with the environmentwhereby a portion of the heat from the environment is absorbed before itreaches the cryogenic supply container.

According to a second aspect of the invention, the cryogenic containeritself incorporates means to generate the Leidenfrost flow in the formof a heater cooperating with structure which guides the cryogenic liquidspheriods and the transporting gas vapor through the supply line.

Additionally, the present invention provides thermostatically controlledmeans for heating the supply conduit means substantially along theentire length thereof from the supply container to a point of use,whereby the Leidenfrost flow is maintained and the conduit is completelyprotected from freezing along the entire extent thereof, independent ofthe particular environmental conditions under which the cryogenic systemis operating.

The present invention also incorporates means for separating the liquidspheroids from the transporting or propelling vapor, which means islocated at the point of use. Thus, no portion of the conduit means issubject to direct contact with the cryogenic liquid and the resultingfrost which would be caused by such contact.

The present invention further provides means to prevent the formation offrost at the structure to be cooled by the cryogenic fluid at the pointof use.

Further objects, features and advantages of the present invention willbecome apparent as the description thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of thepresent invention, reference should be had to the following detaileddescription thereof taken in conjunction with the accompanying drawingwherein the only FIGURE is a schematic of the cryogenic handling systemwith parts thereof illustrated in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing,the cryogenic supply apparatus is generally depicted by the numeral 10and comprises a supply or storage container 12 fabricated of anysuitable material, metallic or nonmetallic. Container 12 is surroundedby a layer 14 of a highly reflective material which functions as aradiation shield. Container l2 and layer 14 are suitably embedded in orsurrounded by an insulating material 16 which may be urethane or anyother suitable material.

Interiorly of container 12 is a chamber 18 in which is stored acryogenic fluid 20 such as liquid nitrogen, hydrogen or the like. Thevapor phase of the cryogenic liquid is located in volume 22 above theliquid level.

A supply conduit 24 delivers cryogenic fluid from a suitable source ofsupply (not illustrated) to chamber 18 through delivery valve 26, acoiled heat shield or heat exchanger tubing 28 embedded in insulation16, and a delivery tube 30 communicating with the vapor space in chamber18. Conventional level sensing probes 32 and 34 are located in chamber18 for developing high and low level signals via lines 36 and 38,respectively, to control the actuation of valve 26 to maintain asubstantially constant level of liquid in container 12. Of course, valve26 may be manually controlled, if desired.

Heat exchange means in the form of a coiled heat shield or tubing 40embedded in insulation 16 has one end in communication with a ventconduit 42 located in the vapor space of chamber 18; the tubing 40 hasits other end in communication with the environment at 44 through apressure control and relief valve 46 of conventional construction. Valve46 functions to maintain a predetermined back pressure in the chamber18.

A cryogenic fluid outlet conduit 48 has one end in communication with adelivery valve 50 adjacent the exterior of apparatus 10. The other endof conduit 48 communicates with a Leidenfrost flow generator depictedgenerally by the numeral 52. Conduit 48 passes through coil 28 in heatexchange relation therewith. The portion of conduit 48 interiorly ofchamber 18 is wrapped with a suitable insulating material 54.

The Leidenfrost generator 52 comprises a conically flared or funnelshaped input 56 adjacent the bottom surface of container 12; the narrowend section 58 of which is in communication with outlet conduit 54, thewide end section 60 of which is in communication with the cryogenicliquid via a plurality of slots or openings 62. A suitable heater 64 islocated adjacent end section 60 in a recess 66 in insulation 16. Heater64 may be of conventional construction such as one of the resistanceheating type, for example.

A suitable baffle 68 is mounted to the wall of container 12 to preventturbulence of the incoming cryogenic fluid from interfering with thegeneration of the liquid spheroid flow through generator 52.

A delivery conduit 70 is in communication with the outlet of valve 50for supplying cryogenic fluid to a point of use depicted generally as72. Conduit 70 may be flexible, semi-rigid or rigid and must beprotected against deterioration by the freezing effects of the lowtemperature cryogenic flow. To this end, heating means 74 is provided inthe form ofa resistance heating wire or coil 76 which is spirallywrapped about the conduit 70 along substantially the entire extentthereof from apparatus 10 to point of use 72. As illustratedschematically, the space between adjacent coils of wire 76 progressivelyincreases from the valve 50 toward the point of use 72. Thus, thequantity of heat supplied to conduit 70 by the heating wireprogressively decreases. The amount of heat required and the exactspacing of the coils will be dictated by the operating conditions aswould be known to those skilled in the art.

Although a heating wire coil has been disclosed, other forms of heatingmeans can be employed. For example, axially extending resistanceelements can be embedded about the peripheral surface of the conduit.These elements can be sized differently to achieve the different heatinputs along the length of the conduit.

One or more heat sensing means, which may comprise thermostats 78 or thelike, are provided in heat exchange relationship with conduit 70.Signals from thermostats 78 are transmitted by lines 80 to a heatercontrol switch or the like 82 which actuates heater 64 via line 84 andheating wires 76 via lines 86.

Point of use 72 may typically comprise an insulated cryogenic fluidcontainer in the form of a dewar or flask 88 which is closed by asuitable cap or stopper 90, through which pass an inlet tube 92, a venttube 94 and a level sensing probe 96. inlet tube 92 communicates withand may be considered a part of conduit 70.

Mounted interiorly of container 88 is a spheroidvapor separator in theform of a conical collector 98 having an upper wide mouthed section 100tapering into a lower narrow mouthed section or opening 102. Thearrangement is such that the cryogenic liquid spheroids S drop throughopening 102 whereas the lighter propelling gas vapor passes through venttube 94. The sphereoids passing through opening 102 collect and form avolume of cryogenic liquid 106, the level of which is maintained byvalve 50 in response to a signal from level sensor 96 via line 108.

Located adjacent the cryogenic liquid 106 and in heat exchangerelationship therewith is the material to be cooled, which may typicallycomprise a light sensitive detector 110 such as an infrared detector. Aspaced observation window or lens 112 is provided for allowing thesensed light to fall upon detector 110.

Vent tube 94 communicates with a conventional relief and regulator valve114 which maintains a predetermined back pressure in dewar 88. Afterpassing through valve 114 the vent vapor is delivered via tube 116 tothe space-between detector 110 and lens 1 l2 and thence to waste vialine 118.

OPERATION In operation, cryogenic liquid is delivered to chamber 18 viatube 30 through coil 28 until probe 32 makes contact with the liquid, atwhich time valve 26 closes. Valve 26 is reopened to deliver more liquidwhen the level drops to the height of probe 34. The cryogenic vapor inspace 22 is exhausted through tube 42 and heat exchanger coils 40through valve 46. Since this vapor is still at a much lower temperaturethan the environment, the vapor will absorb heat from the environmentbefore transmission to the container 12. Thus, the coils 40 effectivelyfunction as a heat shield which, together with the insulation 16 and thereflective layer 14, prevents substantial temperature increases in thecontainer 12.

The application heat from heater 64 adjacent funnel 56 causes thecryogenic liquid to form a two phase or Leidenfrost flow consisting ofliquid spheroids S and a propelling cryogenic vapor which flow is guidedand directed upwardly through funnel 56, insulated section 54, section48 and valve 50 to delivery conduit 70.

To maintain the two phase flow through conduit 70 a controlled amount ofheat must be supplied thereto. This is accomplished by the heating coils76, which function under the influence of thermostats 78 and heatercontrol 82 to supply just the right amount of heat to the conduit tomaintain the proper balance between the liquid spheroid and vapor phaseflowing therethrough. Since some heat may be supplied by theenvironment, the amount of heat supplied by coils 76 is variable withenvironmental conditions. it is however important to note that changingenvironmental conditions can be easily accommodated by simply varyingthe heat output of the coils as by changing the thermostat settings;thereby adding significantly to the versatility of the present system.

As the liquid spheroids are propelled downstream in conduit 70 theyabsorb heat from the surrounding transporting vapor, which in turnabsorbs heat from the conduit walls due to the heat supplied from thecoils 76. To prevent the establishment of a too large vapor to spheroidvolume, it is necessary that less and less heat be supplied further andfurther downstream of valve 50. Thus, the spacing between adjacentheating coils progressively increases from a minimum at valve 50 to amaximum at dewar 88. The exact spacings will depend upon thetemperatures that are to be maintained at the outer peripheral surfaceof conduit 70 which, in turn, are a function of particular system designand particular environmental conditions as would be known to thoseskilled in the art. It has been found that conduit outer walltemperatures in the range of 35F to 100F are suitable.

Upon entry into dewar 88 the two phase flow is separated; the heavierliquid spheroids falling by gravity through funnel 98 and puddling intoa cryogenic liquid volume 106, whereas the lighter vapor rises throughvent tube 94.

The volume of cryogenic liquid in dewar 88 is employed to cool material110 which might typically comprise an infrared detector, which respondsto rays impinging thereupon through window or lens 112. For properoperation, it is imperative that the lens 112 be free of frost so thattransparency thereof is maintained. To this end, the exhaustedpropelling vapor is passed through conduit 116 to the space between thedetector 110 and the lens 112. Since this gas vapor is substantiallyheated to environmental temperature before it reaches the space betweendetector 110 and lens 112, the vapor functions to maintain this space ator near environmental temperatures. The existenceof the same temperatureon both sides of lens 112 will prevent the formation of frost.

Although a preferred embodiment of the present invention has beendisclosed. and described, changes will obviously occur to those skilledin the art. It is therefore intended that the scope of the present.invention is to be limited only by the scope of the appended claims.

What is claimed is:

l. A cryogenic liquid handling system, comprising;

a. storage means for containing a cryogenic fluid,

b. conduit means for conveying said cryogenic fluid from said storagemeans to a point of use,

c. spheroid generator means for developing cryogenic liquid spheroidssurrounded by a gas vapor for propelling said spheroid through saidconduit means, and

d. means for maintaining the flow of said spheroids surrounded by saidgas vapor along substantially the entire extent of conduit means fromsaid storage means to said point of use, said means comprising firstheater means for supplying heat to said conduit means alongsubstantially the entire extent thereof from said storage means to saidpoint of use.

2. The system according to claim 1, wherein;

e. said spheroid generator means is located in said storage means.

3. The system according to claim 1, further comprise. insulating meanssurrounding said storage means,

and

f. heat exchange means embedded in said insulating means forcommunicating the vapor space of said storage means to the environmentwhereby heat from said environment is absorbed by said heat exchangemeans to prevent its absorbtion by said storage means.

4. The system according to claim 1, wherein;

e. said first heater means is attached to said conduit 5 means in such amanner that the heat added thereto progressively decreases from amaximum at said storage means end to a minimum at said point of use end.

5. The system according to claim 4, wherein;

10 f. said first heater means comprises a plurality of resistanceheating elements in surrounding relation to said conduit means.

6. The system according to claim 5, wherein; l 5 g. said heatingelements are helically wrapped about said conduit means. 7. The systemaccording to claim 6, further compriss;

h. heat sensing means responsive to the temperature of said conduitmeans, and

i. heater control means for'actuating said first heater means inresponse to signals from said heat sensing means. 8. The systemaccording to claim 1, further comprise. heat sensing means responsive tothe temperature of said conduit means, and

f. heater control means for actuating said first heater means inresponse to signals from said heat sensing means.

9. The system according to claim 8, wherein;

g. said first heater means is attached to said conduit means in such amanner that the heat added thereto progressively decreases from amaximum at said storage means end to a minimum at said point of use end.

10. The system according to claim 1, wherein;

c. said spheroid generator means comprises a flared frusto-conicalopening in communication with said conduit means and second heater meansadjacent said opening.

11. The system according to claim 10, further comprising;

f. heat sensing means responsive to the temperature of said conduitmeans, and

g. heat control means for actuating said first and second heater meansin response to signals from said heatsensing means.

12. The system according to claim 11, wherein;

h. said first heater means is so related to said conduit means that theheat added thereto progressively decreases from a maximum at saidstorage means end to a minimum at said point ofuse end.

13. The system according to claim 12, wherein;

i. said first heater means comprises a plurality of resistance heatingelements in surrounding relation to said conduit means.

14. The system according to claim 13, wherein;

j. said heating elements are helically wrapped about said conduit means.

15. The system according to claim 1, further com- 65 prising;

e. means for separating said liquid spheroids from said gas vapor atsaid point of use.

16. The system according to claim 15, wherein;

f. said means for separating comprises a funnel shaped member having anopening at the lowermost portion thereof for collecting by gravity theheavier liquid spheroids and a vent tube above said funnel shaped memberfor allowing the lighter gas I vapor to escape therethrough.

17. The system according to claim 1, wherein;

e. said point of use comprises a cryogenic liquid container adapted tocool an infrared detector, and there is further provided;

f. means in said container for separating said cryogenic liquidspheroids from said gas vapor.

18. The system according to claim 17, wherein;

g. said means for separating comprises a funnel shaped member having anopening at the lowermost portion thereof for collecting by gravity theheavier liquid spheroids and a vent tube above said funnel shaped memberfor allowing the lighter gas vapor to escape therethrough.

19. The system according to claim 18, further comprising;

h. an infrared detector assembly in heat exchange relation with saidcryogenic liquid container, said assembly comprising;

i. an infrared detector,

j. a lens spaced from said detector, and wherein;

k. said vent tube communicates with the space between said detector andsaid lens whereby the temperature in said space is brought tosubstantially that of the environment to prevent the formation of froston said lens.

20. A cryogenic liquid handling system, comprising;

a. a cryogenic liquid container,

b. a light sensitive detector in heat exchange relationship with saidcontainer,

c. transparent means spaced from said detector for transmitting lightthereto,

d. a vent tube communicating with said container and the space betweensaid detector and said transparent means whereby the temperature in saidspace is brought to substantially that of the environment to prevent theformation of frost on said transparent means and e. a funnel shapedseparator in said container having and opening at the lowermost portionthereof for collecting by gravity cryogenic liquid flowing into saidcontainer.

21. A cryogenic liquid handling system, comprising;

a. a cryogenic liquid container,

b. conduit means communicating with said container for delivering liquidspheroids surrounded by a gaseous vapor to said container,

0. a funnel shaped separator in said container having an opening at thelowermost portion thereof for collecting by gravity said liquidspheroids, and

d. a vent tube communicating with said container for permitting saidgaseous vapor to escape.

i II

1. A cryogenic liquid handling system, comprising; a. storage means forcontaining a cryogenic fluid, b. conduit means for conveying saidcryogenic fluid from said storage means to a point of use, c. spheroidgenerator means for developing cryogenic liquid spheroids surrounded bya gas vapor for propelling said spheroid through said conduit means, andd. means for maintaining the flow of said spheroids surrounded by saidgas vapor along substantially the entire extent of conduit means fromsaid storage means to said point of use, said means comprising firstheater means for supplying heat to said conduit means alongsubstantially the entire extent thereof from said storage means to saidpoint of use.
 2. The system according to claim 1, wherein; e. saidspheroid generator means is located in said storage means.
 3. The systemaccording to claim 1, further comprising; e. insulating meanssurrounding said storage means, and f. heat exchange means embedded insaid insulating means for communicating the vapor space of said storagemeans to the environment whereby heat from said environment is absorbedby said heat exchange means to prevent its absorbtion by said storagemeans.
 4. The system according to claim 1, wherein; e. said first heatermeans is attached to said conduit means in such a manner that the heatadded thereto progressively decreases from a maximum at said storagemeans end to a minimum at said point of use end.
 5. The system accordingto claim 4, wherein; f. said first heater means comprises a plurality ofresistance heating elements in surrounding relation to said conduitmeans.
 6. The system according to claim 5, wherein; g. said heatingelements are helically wrapped about said conduit means.
 7. The systemaccording to claim 6, further comprising; h. heat sensing meansresponsive to the temperature of said conduit means, and i. heatercontrol means for actuating said first heater means in response tosignals from said heat sensing means.
 8. The system according to claim1, further comprising; e. heat sensing means responsive to thetemperature of said conduit means, and f. heater control means foractuating said first heater means in response to signals from said heatsensing means.
 9. The system according to claim 8, wherein; g. saidfirst heater means is attached to said conduit means in such a mannerthat the heat added thereto progressively decreases from a maximum atsaid storage means end to a minimum at said point of use end.
 10. Thesystem according to claim 1, wherein; e. said spheroid generator meanscomprises a flared frusto-conical opening in communication with saidconduit means and second heater means adjacent said opening.
 11. Thesystem according to claim 10, further comprising; f. heat sensing meansresponsive to the temperature of said conduit means, and g. heat controlmeans for actuating said first and second heater means in response tosignals from said heat sensing means.
 12. The system according to claim11, wherein; h. said first heater means is so related to said conduitmeans that the heat added thereto progressively decreases from a maximumat said storage means end to a minimum at said point of use end.
 13. Thesystem according to claim 12, wherein; i. said first heater meanscomprises a plurality of resistance heating elements in surroundingrelation to said conduit means.
 14. The system according to claim 13,wherein; j. said heating elements are helically wrapped about saidconduit means.
 15. The system according to claim 1, further comprising;e. means for separating said liquid spheroids from said gas vapor atsaid point of use.
 16. The system according to claim 15, wherein; f.said means for separating comprises a funnel shaped member having anopening at the lowermost portion thereof for collecting by gravity theheavier liquid spheroids and a vent tube above said funnel shaped memberfor allowing the lighter gas vapor to escape therethrough.
 17. Thesystem according to claim 1, wherein; e. said point of use comprises acryogenic liquid container adapted to cool an infrared detector, andthere is further provided; f. means in said container for separatingsaid cryogenic liquid spheroids from said gas vapor.
 18. The systemaccording to claim 17, wherein; g. said means for separating comprises afunnel shaped member having an opening at the lowermost portion thereoffor collecting by gravity the heavier liquid spheroids and a vent tubeabove said funnel shaped member for allowing the lighter gas vapor toescape therethrough.
 19. The system according to claim 18, furthercomprising; h. an infrared detector assembly in heat exchange relationwith said cryogenic liquid container, said assembly comprising; i. aninfrared detector, j. a lens spaced from said detector, and wherein; k.said vent tube communicates with the space between said detector andsaid lens whereby the temperature in said space is brought tosubstantially that of the environment to prevent the formation of froston said lens.
 20. A cryogenic liquid handling system, comprising; a. acryogenic liquid container, b. a light sensitive detector in heatexchange relationship with said container, c. transparent means spacedfrom said detector for transmitting light thereto, d. a vent tubecommunicating with said container and the space between said detectorand said transparent means whereby the temperature in said space isbrought to substantially that of the environment to prevent theformation of frost on said transparent means and e. a funnel shapedseparator in said container having and opening at the lowermost portionthereof for collecting by gravity cryogenic liquid flowing into saidcontainer.
 21. A cryogenic liquid handling system, comprising; a. acryogenic liquid container, b. conduit means communicating with saidcontainer for delivering liquid spheroids surrounded by a gaseous vaporto said container, c. a funnel shaped separator in said container havingan opening at the lowermost portion thereof for collecting by gravitysaid liquid spheroids, and d. a vent tube communicating with saidcontainer for permitting said gaseous vapor to escape.